![\"Figure](\"https:\/\/physics.aps.org\/assets\/a8a11ac4-e96f-40f2-a3ba-2631975dfda4\/e147_1.png\")
<\/a><\/p>\nDetermining the entropy of a system typically entails measuring its heat capacity. That approach is harder to apply when the system consists of a very small number of electrons corralled in a tiny device. Fortunately, the entropy of such systems can be derived from the chemical potential, which is the energy needed to pack in an additional electron. This technique enabled the 2018 measurement of the entropy of a single quantum dot, a nanostructure that can trap electrons. Now David Kealhofer of the Swiss Federal Institute of Technology (ETH) Zurich and his collaborators have applied the approach to a double quantum dot [1<\/a>]. Their work provides a stepping stone to future measurements of multiple coupled dots that possess topological or highly entangled states. It could also allow researchers to determine quantities that are even harder to measure, such as exotic quasiparticle couplings.<\/p>\n Kealhofer and his collaborators made their double quantum dot by attaching electrodes to a layered structure of gallium arsenide and aluminum gallium arsenide. The device could be tuned to behave as two isolated dots or as a coupled pair. As the dots were switched from one electron-occupation state to another, the change in entropy could be deduced from the gate voltage at which the two states were equally probable. When an isolated dot was measured, the entropy change for adding a single electron to an empty level, kB log 2, matched both theory and the 2018 measurement. But in the double-quantum-dot regime, when the number of electrons switched from 0 to 1, the researchers found the unexpected value of kB log 3. As more electrons were added or removed from the dot, richer behavior appeared, raising the researchers\u2019 hopes that their technique could detect Majorana zero modes and other exotic states.<\/p>\n \u2013Charles Day<\/p>\n Charles Day is a Senior Editor for Physics Magazine<\/a>.<\/p>\n ReferencesD. Kealhofer et al., \u201cEntropy of a double quantum dot,\u201d Phys. Rev. Lett. 135, 206303 (2025)<\/a>.Entropy of a Double Quantum Dot<\/a><\/p>\n David Kealhofer, Christoph Adam, Max J. Ruckriegel, Petar Tomi\u0107, Benedikt Kratochwil, Christian Reichl, Yigal Meir, Werner Wegscheider, Thomas Ihn, and Klaus Ensslin<\/p>\n Phys. Rev. Lett. 135, 206303 (2025)<\/a><\/p>\n Published November 13, 2025<\/p>\n Subject AreasQuantum Physics<\/a>Nanophysics<\/a>Related Articles A new approach finds useful patterns called quantum scars in the complex dynamics of quantum many-body systems. Read More \u00bb<\/a><\/p>\n<\/a>Quantum InformationQuantum Scars Unmasked<\/a>November 12, 2025<\/p>\n<\/a><\/a> More Articles<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"November 13, 2025• Physics 18, s147 Researchers have taken a step toward using entropy to probe the quantum…\n","protected":false},"author":2,"featured_media":290473,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[49],"tags":[199,79],"class_list":{"0":"post-290472","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-physics","9":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/290472","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/comments?post=290472"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/290472\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media\/290473"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media?parent=290472"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/categories?post=290472"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/tags?post=290472"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}